Unleashing the Mac OS X Genie

Look familiar? The Mac OS X genie effect is a patented effect that is set as the default minimizing effect for windows in the Mac environment. Dating back to 2004, this animation involves a complex transformation of the source window in order to render it correctly on screen. Apple have not documented this feature for use in third party applications in Cocoa (It is available in Carbon). It is something else that makes up the private portion of the Core Graphics framework. However, keen developers like yourself can play with / use / abuse this awesome effect all you like.

The genie effect can be run using the private Core Graphics function CGSCreateGenieWindowAnimation. The requisites for this: A window to use the effect on, a connection to Core Graphics, and another window into which the source window goes. As an example, take a look at this code:

- (void)doGenieFrom:(NSWindow*)source to:(NSWindow*)destination backwards:(BOOL)backwards {
    CGSAnimationRef ref;
    int err;

    err = CGSCreateGenieWindowAnimation(_CGSDefaultConnection(), [source windowNumber], [destination windowNumber], &ref);

    if (backwards) {
        [source orderWindow:NSWindowBelow relativeTo:[destination windowNumber]]; /* No different to makeKeyAndOrderFront]*////
        [source setExcludedFromWindowsMenu:NO];
        [source flushWindow];
    }    
    
    if (0 == err) {
        float x;
        
        for (x = (backwards ? 1.0 : 0.0); (backwards ? (x >= 0.0) : (x <= 1.0)); (backwards ? (x -= 0.01) : (x += 0.01))) {            
            err = CGSSetWindowAnimationProgress(ref, x);
            
            usleep(1000);
        }
        
        err = CGSReleaseWindowAnimation(ref);
        
    }
    
    if (backwards) {
        [destination setExcludedFromWindowsMenu:YES];
    [source makeKeyAndOrderFront:self];
        [source setExcludedFromWindowsMenu:NO];
    } else {
        [source setExcludedFromWindowsMenu:YES];
        
        [destination makeKeyAndOrderFront:self];
        [destination setExcludedFromWindowsMenu:NO];
    }
}

How easy is that? Of course, this only compiles if you #import a header file that defines the Core Graphics private functions. (ie, just add this file to your Xcode project, then add a #import “coregraphicsservices.h” line at the top of the page where you want to use private CGS functions).

In the age of smoking windows, flashing views and an unofficial redefinement of the HIG by developers, the genie animation can finally come out to play.

If you’re enthralled by the genie, here is a list of cool stuff you can do on your mac regarding minimizing windows / expose.

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